Turbocharger internal turbine heat shield having axial flow turning vanes

ABSTRACT

A turbocharger internal heat shield ( 1 ) is provided having axial flow turning vanes ( 2 ). Additionally, the heat shield may have a volute divider wall extender ( 5 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a turbocharger for an internal combustionengine. More particularly, this invention relates to turbocharger havingan axial flow turbine wheel and an internal heat shield having turningvanes. Optionally, for a twin exhaust gas volute the heat shield mayhave a divider wall extender.

2. Description of Related Art

A turbocharger is a type of forced induction system used with internalcombustion engines. Turbochargers deliver compressed air to an engineintake, allowing more fuel to be combusted, thus boosting an engine'shorsepower without significantly increasing engine weight. Thus,turbochargers permit the use of smaller engines that develop the sameamount of horsepower as larger, normally aspirated engines. Using asmaller engine in a vehicle has the desired effect of decreasing themass of the vehicle, increasing performance, and enhancing fuel economy.Moreover, the use of turbochargers permits more complete combustion ofthe fuel delivered to the engine, which contributes to the highlydesirable goal of a cleaner environment.

Turbochargers typically include a turbine housing connected to theengine's exhaust manifold, a compressor housing connected to theengine's intake manifold, and a center bearing housing coupling theturbine and compressor housings together. A turbine wheel in the turbinehousing is rotatably driven by an inflow of exhaust gas supplied fromthe exhaust manifold. A shaft rotatably supported in the center bearinghousing connects the turbine wheel to a compressor impeller in thecompressor housing so that rotation of the turbine wheel causes rotationof the compressor impeller. The shaft connecting the turbine wheel andthe compressor impeller defines an axis of rotation. As the compressorimpeller rotates, it increases the air mass flow rate, airflow densityand air pressure delivered to the engine's cylinders via the engine'sintake manifold.

In a turbocharger, the turbine wheel may be either a radial flow wheelin which the exhaust gas is directed along the radius of the wheel, oran axial flow wheel in which the exhaust gas is directed along the axisof the turbine wheel. Frequently, the bearing housing is shielded fromthe heat of the exhaust gases by a heat shield which is placed betweenthe turbine wheel and the bearing housing.

U.S. Pat. No. 7,631,497 relates to a turbocharger with a heat shieldpositioned between the turbine wheel and the bearing housing, whereinthe heat shield defines a gap between the turbine wheel. and the heatshield and is provided with at least one rib extending into the gap. Inthis gap, in the case of a conventional flat heat shield, the turbinewheel backface may act in the manner of a centrifugal pump, pumping gasout from within the gap, creating a region of reduced pressure adjacentthe outboard side of the turbine shaft bearing, and drawing oil out theshaft bearing and into the space between the turbine wheel backface andthe heat shield. The inventive heat shield has raised structuresdesigned to interfere with the rotational and centrifugal flow of gas inthe gap between heat shield and turbine wheel backface, thus prevent oilbypass.

U.S. Pat. No. 6,739,134 relates to an exhaust-gas turbocharger for aninternal combustion engine having a turbine in the exhaust-gas tract anda compressor, driven by the turbine, in the intake tract, the turbinehaving a flow channel with a radial flow-inlet cross-section and asemi-axial flow-inlet cross-section, and a flow ring being providedwhich limits the two flow-inlet cross-sections. The turbine is furnishedwith variable turbine geometry for the changeable adjustment of theflow-inlet cross-section. To improve efficiency, the position of theflow ring in the housing of the exhaust-gas turbocharger is variablyadjustable.

SUMMARY OF THE INVENTION

In many turbochargers the exhaust gas volute conveys the exhaust gas tothe turbocharger in a direction which is radial to the turbine wheel. Inturbochargers having an axial turbine wheel, it is necessary to turn theexhaust gas to the axial direction before it gets to the turbine wheel.It has been discovered that a heat shield having turning vanes may beused to redirect or guide the exhaust gas before it gets to the turbinewheel.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will be readily appreciated as thesame becomes better understood by reference to the following detaileddescription when considered in connection with the accompanying drawingswherein:

FIG. 1 shows a heat shield with turning vanes;

FIG. 2 shows a heat shield with turning vanes and a volute divider wallextender; and

FIG. 3 shows a heat shield, and a volute having a divider and a dividerwall extender.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows a heat shield (1) with turning vanes (2).

FIG. 2 shows a heat shield (3) with turning vanes (4) and a volutedivider wall extender (5).

FIG. 3 shows a heat shield (6), a volute (7), with a divider wall (8)and a volute divider wall extender (9).

The exhaust gas from the engine is conducted to the turbine housing bythe exhaust gas volute (7). The exhaust gas volute (7) allows theexhaust gas to enter the turbine housing in a direction which is radialto the turbine wheel. If an axial turbine wheel is being used, the gasmust be turned to an axial direction before it arrives at the turbinewheel. Exhaust gas directed toward a flat bearing housing face will turnto the axial direction. Often a heat shield (1) and (3) is placed overthe wall of the bearing housing to shield the bearing housing from thehot exhaust gases. Exhaust gases directed toward the heat shield (1) and(3) will turn to the axial direction. However, it has now beendiscovered that vanes (2) and (4) in the heat shield (1) and (3) wallwill efficiently redirect the exhaust gas from the radial to the axialdirection. The vanes (2) and (4) guide the exhaust gas along the wall ofthe heat shield (1) and (3) and thereby optimize the angle of incidenceon the turbine wheel blades' leading edges. Instead of relying on thenatural vectors of the gas leaving the housing volute and the turningvector imposed by the heat shield surface, addition of the turning vanes(2) and (4) can force the gas incidence angle to be more optimized forwhat the wheel blade angles are expecting. By better organizing the flowinto a more specific flow vector, improved efficiency is achieved. Thenumber of vanes can vary. Four to eight turning vanes has been found tobe satisfactory.

In multi-cylinder engines, cylinders from opposing banks firealternatively. In the case of a “V” engine the banks are separatedacross the engine. In the case of an inline engine, the banks couldsimply be the front half of cylinders versus the back half of cylinders.The exhaust gas is conducted to turbine housing in separated portions ofthe volute. The separate gas streams serve to preserve the pulse ofpressure which occurs when the exhaust gas is released from thecylinder. The preservation of the pulses is desirable because the extrapulse of pressure can start the turbine moving faster. This is helpfulin reducing turbo lag. In the region where the exhaust gases areadmitted to the turbine housing, a separator or divider wall (8) betweenthe two halves of the volute can help preserve the separation betweenexhaust gases from each cylinder bank, and thus maintain the pressurepulses. A drawback of using an axial flow wheel and a heat shield in aturning arrangement is that the wheel is now spaced far away from theturbine housing, and hence far away from the housing divider wall (8)and the pulse separation. By adding a divider wall extension (5) and (9)to the heat shield, the preservation of pulses can be maintained all theway downstream to the wheel inlet.

While the invention has been shown and described with respect to theparticular embodiments, it will be understood by those skilled in theart that various changes and modifications may be made without departingfrom the scope of the present invention as defined in the followingclaims.

What is claimed:
 1. A heat shield (1) for use in a turbocharger havingan axial flow turbine wheel, having turning vanes (2) which turn theflow of exhaust gas to the axial direction.
 2. A heat shield (1)according to claim 1 having 4 to 8 turning vanes (2).
 3. A heat shield(1) according to claim 1 having 7 turning vanes (2).
 4. A heat shield(1) according to claim 1 further comprising a volute divider wallextender (5).